You can look at what I’ve done in one of my slides: http://slides.klipse.tech/asciidoc/klipse-clojure.html#slide-22
The rule should be
.hidden {
visibility: hidden;
height: 0px;
}
My solution is better :-P
Seriously the visibility rule is poorly supported and my rule is the correct / most widely supported way to implement the desired behaviour as well as being the simplest and most concise